Instruction Manual MM850481 ed. 03a
12
4 PRINCIPLE
OF
OPERATION
The
EGA4
analyzer is based on the following functional blocks:
MicroController
Impact printer
Keyboard
Display
250
memory
Power supply
Li-Ion battery
Battery charger input
External probe input
Pt100 Tair input
Gas outlet
P2 -
'
P
P1 – Draft/Pressure
Differential
pressure
sensor
Gas input
INLET
Pump
1° Sensoe O2
3° Sensor
TcK Tgas input
Water trap
Line filter
IR serial port
2° Sensor CO
4° Sensor
4.1 Measurement
principle
The gas is sampled and aspirated through the probe with a primary pump powered at constant voltage.
To position the sampling probe in the exhaust gas pathway a hole of 11mm, up to 16mm, should be drilled and the retaining
cone of the sampling probe firmly screwed in it.
The retaining screw in the cone enables the probe to be easily moved to locate the core flow, normally correspondent to the
center of the section of the smoke tube. The flue gas and exhaust gas pathway, should be checked for gas-tightness before
carrying out a measurement and, if necessary, non gas-tight points should be sealed.
The O
2
sensor is essentially an electrochemical cell, with two electrodes and electrolyte solution. The behavior is similar to a
normal battery and therefore the sensitivity decreases with time. The expected life does not relate to the operative time and is
lost after approximately 24 months.
The toxic gas measurements (CO, SO
2
, NO and NO
2
) use electrochemical cells, with an expected operative life of 3 years.
The electrochemical cell grants accurate results for time intervals of approximately 60 minutes. The zero drift is automatically
corrected by the instrument every time the instrument is switched-on, using fresh ambient air as reference. This operation
should be made with the sampling probe not inserted in the chimney or with the sampling probe pneumatic connector
disconnected from the analyzer gas inlet.
When a long time analysis has to be made, a new autozero procedure should be performed.
The pressure/draught sensor is based on the principle of the extension metric measuring bridge. When the instrument is
switched-on, a zero calibration of the draught/pressure circuit is also executed. Leave open the “
'
P” connector during this
phase.
Measured and calculated parameters are indicated on a LCD alphanumeric display (40x56 mm), equipped with a automatic
back light device for easy readings, also in poor light conditions.
